1. Field of the Invention
The subject invention relates to pressure and other transducers, and to overload protection systems for transducers or for diaphragms in general.
2. Disclosure Statement
The following disclosure statement is made pursuant to the duty of disclosure imposed by law and formulated in 37 CFR 1.56(a). No representation is hereby made that information thus disclosed in fact constitutes prior art, inasmuch as 37 CFR 1.56(a) relies on a materiality concept which depends on uncertain and inevitably subjective elements of substantial likelihood and reasonableness and inasmuch as a growing attitude appears to require citation of material which might lead to a discovery of pertinent material though not necessarily being of itself pertinent. Also, the following comments contain conclusions and observations which have only been drawn or become apparent after conception of the subject invention or which contrast the subject invention or its merits against the background of developments which may be subsequent in time or priority.
There are a multitude of transducers and similar devices employing diaphragms or deflectable beams in their operation. By way of example, reference may be had to the force transducer disclosed in U.S. Pat. No. 3,341,796, by W. H. Eisele, issued Sept. 12, 1967 and proposing a diaphragm stop adjustable by a threaded sleeve lockable with a hexagonal nut, to the beam-type transducers disclosed in U.S. Pat. Nos. 3,970,982 and 4,051,451, by A. D. Kurtz et al, issued July 20, 1976 and Sept. 27, 1977, respectively, and proposing the use of gross stops, the strain gage of U.S. Pat. No. 3,365,689, by A. U. Kutsay, issued Jan. 23, 1968, and proposing that a transducer body be so formed that a lower face thereof forms in the unstressed condition a desire gap between itself and an adjacent portion of the apparatus, whereby automatic overload protection was believed to be possible, to the pressure measuring instrument of U.S. Pat. No. 3,377,866, by D. J. Flavin, issued Apr. 16, 1968, and proposing the provision of a central block to form a stop for limiting movement of a stress-responsive device, to the flexible structure of U.S. Pat. No. 3,433,064, by W. E. Jacobson, issued Mar. 18, 1969, and proposing formation of a stop member out of a wall portion, and to the transducer overload protection overload system of U.S. Pat. No. 3,537,318, by R. P. Helin, issued Nov. 3, 1970, and proposing provision of a screw-adjusted stop.
Reference may also be had to various folded beam and similar structures, such as those shown in U.S. Pat. Nos. 2,859,613, by M. Green, issued Nov. 11, 1958, and showing a multiple bending beam force measuring device, 3,222,628, by H. S. Pien, issued Dec. 7, 1965, and disclosing a force measuring device, 3,484,732, by R. W. Postma, issued Dec. 16, 1969, for a dual range pressure sensor, and 3,553,625, by C. K. Stedman, issued Jan. 5, 1971 and disclosing a side-sensitive miniaturized pressure transducer.
In practice, folded beam structures are very sensitive against overload and cannot simply be protected by a stop acting on the unilaterally fixed beam of the folded beam assembly. Reference may in this respect be had to U.S. Pat. No. 4,199,980, by Ronald Bowman, one of the present coinventors, issued Apr. 29, 1980, for folded beam structure utilization methods and apparatus. In particular, that patent provides a stop system which works fine for folded beam structures and avoids the problems of previous attempts and proposals. That stop system also provides overload protection for diaphragms in many situations.
Particularly in larger transducers or in other diaphragm systems exposed to heavier loads, an overload protection system at the diaphragm itself is still desirable. Accordingly, resort has been had to screw-type or similar threaded stop system. Such systems, in practice, are, however, expensive in their implementation and require access to the assembled transducer structure for adjustment purposes. Also, there are vibration-type and other situations where use of threaded adjustment devices is undesirable or unacceptable.